He said some people may "question the wisdom" of choosing him, but said the Conservatives have historically had the "best insights" into human nature and how to build a great society.

"At this pivotal moment in history," Johnson said, they had to match the desire for partnership with Europe and the simultaneous desire for "democratic self-government in this country".

He said he looked at the party members that morning and saw them not daunted by Brexit.

"We know we can do it and the people of this country are trusting we can do it," he said. "We are once again going to believe in ourselves... we are going to unite this amazing country."

Johnson also praised Hunt as a "formidable opponent" with "excellent ideas, all of which I propose to steal forthwith".

Johnson faces immense challenges in his new role due to his government’s tiny working majority in an increasingly fractious Parliament.

Theresa May was expected to take questions in Parliament for the last time as prime minister on Wednesday, after which she will go to Buckingham Palace to resign, followed shortly by Johnson who would be officially given his title by the Queen.

Johnson will then start to assemble his Cabinet – but he could be interrupted on Thursday with a call to Parliament if Jeremy Corbyn’s opposition decides to test whether Johnson’s government can still command a majority in a confidence vote.

If he loses, an election could be called within weeks – though Labour is reportedly most likely to keep its powder dry, because it doesn't want to risk giving Johnson an early victory but rather give potential Tory rebels time to consider their options as the Brexit deadline looms.

Johnson is likely to hold early talks with the Northern Irish DUP, who have promised to support the Conservatives in a confidence vote, but are likely to demand fresh promises from Johnson over Brexit.

And even including the DUP, Johnson’s working majority in Parliament is just four MPs, leaving every part of his agenda at the mercy of a few disgruntled backbenchers.

Johnson has made significant unfunded promises during his leadership campaign, with tax cuts and other pledges totting up to tens of billions of pounds.

Johnson will have to deal with tensions within his party, still deeply divided over Brexit.

He won the leadership by pledging to renegotiate the Withdrawal Agreement that May struck with the EU – and to hold the threat of a no-deal Brexit over the EU’s heads if a new deal is not struck by October 31.

But the EU has insisted repeatedly the agreement is not up for renegotiation, and believe Johnson’s so-called solution involves ideas they have already rejected as unworkable, added to a cherry-picking approach that would be unacceptable to EU member nations.

A famous Johnson quote is that his “policy on cake is pro having it and pro eating it”.

With the October 31 deadline looming, Johnson is unlikely to strike a new deal in that time – leaving delay or no deal the only realistic options. He has repeatedly rejected yet another delay.

A significant number of Conservative MPs have indicated they would vote in Parliament to try to block a no-deal exit, which is forecast to bring a global financial crisis-level hit to the British economy and industry.

Current Chancellor Philip Hammond has said he would resign on Wednesday afternoon – before Johnson became prime minister – in a symbolic move flagging his intention to oppose Johnson if he pushes for a no-deal exit.

Hammond has hinted that he could vote against the government in a confidence vote if it was necessary to stop a no-deal Brexit, which he said was “not something I could ever sign up to”.

Hammond was expected to be joined by other ministerial resignations including Justice Secretary David Gauke and International Development Secretary Rory Stewart. Foreign minister Alan Duncan resigned on Monday, warning a “dark cloud of Brexit” was damaging Britain’s international standing and potential.

And education minister Anne Milton resigned on Tuesday, citing "grave concerns" over the possibility of leaving the EU without a deal.

Other Tory MPs including former attorney-general Dominic Grieve have even suggested they could leave the party if Johnson became prime minister.